1. Field of the Invention
This invention relates to apparatus and methods for locating, catching and raising certain freshwater aquatic organisms, and more particularly, but not by way of limitation, to methods of locating, catching and raising certain species of fish.
2. Description of the Prior Art
Certain environmental parameters are known to exert influence upon aquatic organisms. The influence of a given parameter is different upon different species of aquatic organisms. For a given environmental parameter and a given species of organism, the influence of that parameter on the species can be described by two concepts. These concepts are requirements and tolerances. The concept of requirements relates to the necessary range of the given parameter for the viability of the species in metabolism, growth and reproduction. The concept of tolerances relates to the extreme limits of the given parameter in which the species can live, but in which the species cannot survive indefinitely and cannot grow or reproduce.
Three environmental parameters which have heretofore been recognized as influencing the behavior of certain gilled aquatic organisms are salinity, dissolved oxygen concentration and temperature. Salinity, as used in this context, is the concentration of dissolved solids present in the water and is expressed in parts per million (ppm). Dissolved oxygen concentration is also expressed in parts per million.
More particularly, these three parameters have been found to behaviorally influence certain species of fish. For example, most pelagic fish--fish which are for the most part active free swimmers, such as shad, white bass and striped bass--are organisms which require a considerable amount of oxygen--around 8 ppm--to maintain an active metabolism. That is, they require dissolved oxygen concentrations of that level to be physically active and to grow and reproduce. However, they can tolerate dissolved oxygen concentrations of 6 ppm and below, though they cannot grow and reproduce at such low oxygen concentrations.
The presence or absence and the nature of physical structure (tree limbs and the like) in the water is known to be another environmental parameter influencing the behavior of fish.
The reasons for which a given species of fish requires and seeks out an environment having certain values of these parameters are not precisely known, but it is known that in the case of oxygen, salinity and temperature, the reasons have to do with the metabolism and body chemistry of the species. The species does not possess the capacity to regulate its body temperature and chemistry independent of its environment, but it can sense the presence of favorable or unfavorable environmental conditions, and can and does seek out an environment with favorable conditions to permit it to maintain its metabolism and body chemistry at the levels required for viability. For example, fish are cold-blooded--that is, their body temperature is dependent upon the temperature of their environment. Fish therefore tend to seek out an environment with water temperature near their preferred body temperature. The most desirable temperature for bass, for example, is from 65.degree. F. to 75.degree. F.
This tendency of certain species of fish to seek out an environment having preferred values of salinity, temperature and dissolved oxygen concentration has been previously recognized by icthyologists, and has been the basis of apparatus and methods for locating, catching and raising fish.
In the commercial raising of certain aquatic organisms, including fish, it has been recognized that the growth rate and general health of the organisms can be enhanced by maintaining the preferred values of one or more of these environmental parameters.
The location and catching of aquatic organisms from their natural environment have long been achieved by methods based in large part upon first locating those areas of the environment most attractive to the organisms, and in more recent methods, having the values of the aforementioned parameters which have been found to be preferred by the particular species of organism being sought.
In particular, very significant commercial success has been realized by manufacturers of apparatus suitable for determining the dissolved oxygen concentration and the temperature of the water in forms suitable for sale to, and use by, sportsmen in quest of various species of freshwater game fish. However, such devices and methods have not been entirely successful. Often fish have been found, for example, in areas of relatively low dissolved oxygen concentration, even though their metabolic demand is not thereby optimally satisfied. Sometimes they have been found in areas of temperature or salinity with values of those parameters very much different from what are known to be the preferred values for the species being observed. Occasionally, a given species has been found in an environment in which values of all three of the aforementioned parameters are very much different from its preferred values, and sometimes a species has been observed to actually avoid areas having desirable values of all three parameters and instead to inhabit areas with less desirable temperature, salinity and dissolved oxygen concentration.